How many millilitres of 0.200 M NaOH are required to completely neutralize 20.0 mL of 0.100 M HCl?

• A. 10.0 mL
• B. 20.0 mL
• C. 5.00 mL
• D. 10.0 mL

Answer: (A)

Verified step by step guidance

1. Write the balanced chemical equation for the neutralization reaction: \(\mathrm{HCl} + \mathrm{NaOH} \rightarrow \mathrm{NaCl} + \mathrm{H_2O}\).
2. Calculate the moles of HCl present using the formula: \(\text{moles} = M \times V\), where \(M\) is molarity and \(V\) is volume in liters. For HCl, this is \$0.100\,M \times 0.0200\,L$.
3. Since the reaction is a 1:1 mole ratio between HCl and NaOH, the moles of NaOH required to neutralize the acid are equal to the moles of HCl calculated.
4. Use the moles of NaOH and its molarity to find the volume of NaOH needed: \(V = \frac{\text{moles}}{M}\), where \(M\) is the molarity of NaOH (0.200 M).
5. Convert the volume of NaOH from liters to milliliters by multiplying by 1000 to get the final answer in milliliters.